1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
|
using System;
using Org.BouncyCastle.Crypto.Macs;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.Utilities;
namespace Org.BouncyCastle.Crypto.Generators
{
public class KdfCounterBytesGenerator : IMacDerivationFunction
{
private static readonly BigInteger IntegerMax = BigInteger.ValueOf(0x7fffffff);
private static readonly BigInteger Two = BigInteger.Two;
private readonly IMac prf;
private readonly int h;
private byte[] fixedInputDataCtrPrefix;
private byte[] fixedInputData_afterCtr;
private int maxSizeExcl;
// ios is i defined as an octet string (the binary representation)
private byte[] ios;
// operational
private int generatedBytes;
// k is used as buffer for all K(i) values
private byte[] k;
public KdfCounterBytesGenerator(IMac prf)
{
this.prf = prf;
this.h = prf.GetMacSize();
this.k = new byte[h];
}
public void Init(IDerivationParameters param)
{
KdfCounterParameters kdfParams = param as KdfCounterParameters;
if (kdfParams == null)
{
throw new ArgumentException("Wrong type of arguments given");
}
// --- init mac based PRF ---
this.prf.Init(new KeyParameter(kdfParams.Ki));
// --- set arguments ---
this.fixedInputDataCtrPrefix = kdfParams.FixedInputDataCounterPrefix;
this.fixedInputData_afterCtr = kdfParams.FixedInputDataCounterSuffix;
int r = kdfParams.R;
this.ios = new byte[r / 8];
BigInteger maxSize = Two.Pow(r).Multiply(BigInteger.ValueOf(h));
this.maxSizeExcl = maxSize.CompareTo(IntegerMax) == 1 ?
int.MaxValue : maxSize.IntValue;
// --- set operational state ---
generatedBytes = 0;
}
public IMac GetMac()
{
return prf;
}
public IDigest Digest
{
get { return prf is HMac ? ((HMac)prf).GetUnderlyingDigest() : null; }
}
public int GenerateBytes(byte[] output, int outOff, int length)
{
int generatedBytesAfter = generatedBytes + length;
if (generatedBytesAfter < 0 || generatedBytesAfter >= maxSizeExcl)
{
throw new DataLengthException(
"Current KDFCTR may only be used for " + maxSizeExcl + " bytes");
}
if (generatedBytes % h == 0)
{
generateNext();
}
// copy what is left in the currentT (1..hash
int toGenerate = length;
int posInK = generatedBytes % h;
int leftInK = h - generatedBytes % h;
int toCopy = System.Math.Min(leftInK, toGenerate);
Array.Copy(k, posInK, output, outOff, toCopy);
generatedBytes += toCopy;
toGenerate -= toCopy;
outOff += toCopy;
while (toGenerate > 0)
{
generateNext();
toCopy = System.Math.Min(h, toGenerate);
Array.Copy(k, 0, output, outOff, toCopy);
generatedBytes += toCopy;
toGenerate -= toCopy;
outOff += toCopy;
}
return length;
}
private void generateNext()
{
int i = generatedBytes / h + 1;
// encode i into counter buffer
switch (ios.Length)
{
case 4:
ios[0] = (byte)(i >> 24);
goto case 3;
// fall through
case 3:
ios[ios.Length - 3] = (byte)(i >> 16);
// fall through
goto case 2;
case 2:
ios[ios.Length - 2] = (byte)(i >> 8);
// fall through
goto case 1;
case 1:
ios[ios.Length - 1] = (byte)i;
break;
default:
throw new InvalidOperationException("Unsupported size of counter i");
}
// special case for K(0): K(0) is empty, so no update
prf.BlockUpdate(fixedInputDataCtrPrefix, 0, fixedInputDataCtrPrefix.Length);
prf.BlockUpdate(ios, 0, ios.Length);
prf.BlockUpdate(fixedInputData_afterCtr, 0, fixedInputData_afterCtr.Length);
prf.DoFinal(k, 0);
}
}
}
|
